Plant Physiol, July 2001, Vol. 126, pp. 1129-1138
An Insight into Cell Elasticity and Load-Bearing Ability.
Measurement and Theory
Chunfang
Wei,*
Philip M.
Lintilhac, and
Jason J.
Tanguay
Department of Botany, Marsh Life Science Building, University of
Vermont, Burlington, Vermont 05405-0086 (C.W., P.M.L., J.J.T.); and
Department of Physics, Guangxi National University, 530006, China
(C.W.)
We have studied the elasticity and load bearing ability of plant
tissue at the cellular level, using onion (Allium cepa)
epidermal cells. The Young's modulus and Poisson's ratio of the cells
were obtained by loading a tensile force on onion epidermal peels of different turgor pressures, and measuring the elongation and the lateral contraction of the peels. The Young's moduli and the
Poisson's ratios ranged from 3.5 to 8.0 MPa and 0.18 to 0.30, respectively. To determine the effects of cell elasticity and turgor
pressure on the cell's ability to bear load, we loaded a small glass
ball onto a cell and measured the projected contact area between the ball and the cell. Unlike previous studies, we considered the cell as a
whole entity, and utilized the Boussinesq's solution to derive the
relevant equations that related the elastic parameters and cell
deformation. For cells with a turgor pressure 
0.34 MPa, the
predicted contact area agreed well with the measured area. The
equations could also predict cell turgor pressure with a deviation from
the measured value of 0.01 MPa. This study gives strong support to ball
tonometry, a new method of measuring cell turgor pressure.
*
Corresponding author; e-mail cwei{at}zoo.uvm.edu; fax
802-656-0440.
© 2001 American Society of Plant Physiologists
